The present invention relates to temperature controls, and more particularly to temperature controls for vehicle cabins.
A wide variety of controls has been developed for regulating the temperature within the cabin of a vehicle such as a truck tractor or agricultural vehicle. Such temperature controls improve the comfort of the cabin by maintaining the temperature at or near a preselected value.
One particularly efficient air conditioning temperature control has been previously sold by the assignee of the present application. This control includes a thermostat portion outputting a signal indicative of the relation between a selected temperature and the actual temperature within the cabin and an output circuit responsive to the thermostat portion for powering the air conditioner compressor clutch when cooling is required. Although this control constituted a noteworthy advance in vehicle cabin controls, it was not without its drawbacks. Perhaps most importantly, this control applied electrical power to the compressor clutch whenever the actual cabin temperature exceeded the desired cabin temperature. Consequently, if a short-circuit condition existed within the compressor clutch circuit, this control continued to apply power to the clutch, possibly causing the clutch to burn out. Such possibility is, of course, undesirable in a commercial deployment.